Several devices are known in the art for determining physical characteristics of articles using light. Most common are devices which employ a light emitter and detector, and which provide a digital indication of the presence or absence of an object if it breaks the path between the emitter and detector. For example, in U.S. Pat. No. 4,571,498, two perpendicularly disposed arrays of such light detector/emitter pairs are used to determine the rough shape of an object. Such devices are of limited utility because only one object may be in the path between the light detectors and emitters, and placing many objects in single file for scanning can cause a significant backlog in production operations.
More germane to the present invention are devices which use light reflected from the surface of an article to determine certain characteristics of the article. For example, in U.S. Pat. No. 4,276,983, light reflected from an article is used to determine the color of the article. The device disclosed therein may be used to sort beans based on color. In U.S. Pat. No. 4,450,352, expected and regular surface contour changes are detected by employing several light detectors strategically placed so that the contour changes affect the light sensed by the light detectors. U.S. Pat. No. 4,456,829 discloses a device for determining the distance from a light detector to a reflective surface by comparing emitted light to a reference beam by use of a rotating scanner. U.S. Pat. No. 4,510,504 discloses a device for detecting a deflection amount of ink by projecting light on a flying ink drop, and detecting the extent of deflection of the ink drop based on the behavior of the light reflected by the ink drop. Multiple light detectors may be used to determine the extent of deflection.